1. Field of Invention
The present invention relates to a method and apparatus for injecting a chemical into a process flow media; and more particularly relates to a method and apparatus for injecting a chemical into a process flow media upstream of an inline mixer.
2. Description of Related Art
FIG. 1 shows a simple method of injecting a chemical into a process flow media upstream of a dynamic mixer (see FIG. 4) in which the chemical flow generally indicated as F is introduced using a pipe 10 that joins a main process piping 12 in a perpendicular or angled fashion. Generally, the chemical injection piping 10 is arranged perpendicular to the main process piping 12 and is smaller in diameter than the main process piping 12. The chemical injection piping 10 may be introduced anywhere around the circumference of the main process piping 12 (i.e. the bottom, top or side). However, the method of adding the chemical flow using a perpendicular or angled connection does not introduce the chemical at the location for optimal mixing performance by the mixer rotor and stator blade configuration. The optimal location for entry into the mixer is the zone of highest shear and turbulence; this zone is generally not adjacent to the process piping walls. The addition of chemicals into a less than optimum location results in high and low concentrations of chemical, resulting in the need to add additional chemicals or accept less than desired mixing performance.
FIG. 2 shows a second method of injecting a chemical into a process flow media that utilizes single or multiple orifice plates 20, 22 in a main processing pipe 26. The orifice plates 20, 22 are used to create turbulence generally indicated as T to the flow generally indicated as F and initiate mixing of the chemical before entering the dynamic mixer (see FIG. 4). The chemical may be in an injection pipe 28 arranged introduced upstream, downstream of a single orifice plate 20 or 22 or may be introduced between a set of orifice plates 20, 22, as shown. The orifice plates 20, 22 may or may not be concentric with the inside of the main process piping 26. However, using orifice plates 20, 22 to add turbulence and mix the chemical before entering the inline mixer distributes the chemical and some of the chemical enters the mixer rotor (see FIG. 4) at less than optimal locations, such as areas of low shear and turbulence. Also, adding the chemical using orifice plates 20, 22 allows some of the chemical to bypass the mixer rotor (see FIG. 4) by passing around the outside of the mixer rotor. The orifice plates 20, 22 also create a large undesirable pressure drop in the process line, this pressure drop creates a requirement for additional pump pressure.
Other methods use plates or pipes with small holes to distribute the chemical. Again, these methods do not introduce the chemical to the optimal mixing location and many times are prone to plugging.
In view of this, there is a need in the industry for an improved inline mixer architecture to that known in the art.